Factual error: When Rambo plays possum then suddenly takes out the Russian officer's Hind Helicopter he uses an M72A2 light anti-tank weapon (LAW). When fired, the M72A2 has a back blast that can kill out to 100 feet, which means he would have either blown up his own helicopter or killed all the MIA's he had rescued...
Factual error: Near the beginning of the film, the airplane that will fly Rambo into the jungle is being refueled and prepared for takeoff. Ericson shines his flashlight into one of the jet exhaust ports to inspect it, an impossible task since the jet engines have already been started. Not even Rambo would be able to stand behind a jet exhaust without getting blown over or burnt to a crisp.
Factual error: It is completely implausible that Rambo, an experienced green beret would be careless enough to get his gear caught in the plane while jumping out. Also even if he had gotten got, soldiers carry their gear in different layers that are quickly releasable via strap or clip just in case they do get stuck. Rambo would not have gotten stuck, and if he did he could detached his his gear easily and without all the drama.
Factual error: In the shot where Rambo is blowing up everything in sight from the Huey, there's a quick moment when it is seen from the front. The chopper has two seven tube rocket launchers, and after he fires all the rockets, there are trailing wires on the starboard pod. This is wrong because these launchers, as well as the nineteen tube model, fire 7.65 inch rockets that are electrically primed and fired from a contact pin in the rear, so no external wiring exists. Also, after he fires all the rockets, and therefore has no more, in the next shot, the launchers are loaded again.